I. Field of the Invention
The present invention relates generally to medical instruments and, more particularly, to an endoscope.
II. Discussion of Related Art
Laparoscopic surgery has enjoyed increasing acceptance, particularly for surgery involving the abdominal cavity. In such surgery, one or more incisions are made through the patient""s skin. Thereafter, various medical instruments, including endoscopes, are inserted through the incisions and into a body cavity, such as the abdominal cavity.
In order for the surgeon to see into the abdominal cavity, the surgeon typically uses an endoscope which is inserted through a cannula and into the abdominal cavity. The previously known endoscopes typically comprise an elongated tube having one or more fixed lenses. These lenses provide an optical view of the interior of the body cavity to an eyepiece or other display means accessible to the surgeon outside the body. Illumination for the endoscope is typically provided by optical fibers which extend along the length of the endoscope and form a ring around the outer periphery of the free end of the endoscope. The opposite ends of the optical fibers are connected to a light source.
These previously known endoscopes, however, have all suffered from a number of disadvantages. Perhaps the most significant disadvantage of these previously known endoscopes is that, since the optical lenses are fixed within the endoscope, the field of magnification for the endoscope remains constant. Typically, these previously known endoscopes utilize lenses which provide low or macroscopic magnification (hereafter collectively referred to as macroscopic magnification) within the body cavity so that a relatively wide field of view of the body cavity is obtained.
In many situations, however, it would be desirable for the endoscope to provide microscopic magnification of organs contained within the body cavity. For example, in certain situations where cancerous growths within body organs are suspected, the macroscopic magnification provided by the previously known endoscopes is insufficient to examine the organ tissue in sufficient detail to determine whether the tissue abnormality is cancerous or benign. As a result, it has been necessary for the surgeon to remove the tissue to perform a biopsy and, in many cases, to remove the entire organ for subsequent pathological examination outside the body.
The removal of biological tissue from the body and subsequent pathological examination outside the body suffers from two important disadvantages. First, in the event that the organ abnormality is benign, the biopsy and possible removal of the entire organ from the body results in unnecessary harm and even loss of organ function to the patient. Second, since the subsequent pathological examination of the body tissue oftentimes occurs long after the end of the operation, in the event that the pathological examination reveals a cancerous growth within the body tissue, it is oftentimes necessary for the surgeon to re-enter the body cavity and remove additional body tissue in an attempt to completely eradicate the cancer. This disadvantageously, however, subjects the patient to a second operation.
An additional disadvantage of previously known endoscopes is that the illumination and viewing paths are separate and each path uses only a portion of the available diameter of the endoscope. It would be desirable to use the entire available diameter of the endoscope for the viewing path as it would permit the use of optical lenses with larger apertures, thus providing increased resolution in the optical image formed by the lenses without requiring an increase in the overall diameter of the endoscope.
The present invention provides an endoscope for use in laparoscopic surgery which overcomes all of the above-mentioned disadvantages of the previously known devices.
The endoscope of the present invention has a lens assembly forming an optical path within an endoscope tube, in which the optical path is shared by both the light used to illuminate an object, such as tissue within a body cavity, and the light collected from the object. The endoscope tube is joined to an external housing that has an additional optical assembly; the combined endoscope tube and housing optics form images on one or more detectors within the housing that convert the images into electronic signals. Cables are provided for an electronic and optical interface between the housing and an external control system such as a personal computer, power supplies, and illumination sources.
The magnification achieved by the endoscope assembly can be varied between macroscopic, or low, magnification and microscopic, or high, magnification. Macroscopic magnification is utilized to provide an optical view to the surgeon of a relatively wide area within the body cavity whereas in the microscopic magnification mode, the system is capable of resolving structure at the cellular level. In microscopic mode, the system provides high resolution imaging not only of the surface layer of body tissue, but also of layers beneath the surface by means of a confocal assembly contained within the housing. In-depth imaging is enhanced by the use of near-infrared illumination, at which wavelengths body tissue is typically more transparent than at visible wavelengths.
The optical assembly in the housing includes separated or partially separated paths for the macroscopic and microscopic imaging modes. Beamsplitters are provided to split the combined optical path of the endoscope lens into the separated paths of the housing optics, and optionally to recombine the paths onto a single CCD camera. The macroscopic magnification path uses white light illumination and preferably a three-chip CCD detector to provide full color imaging. The light source used in the microscopic magnification mode is preferably a laser diode operating in the near infrared region of the spectrum at a wavelength of about 950 nm. The microscopic magnification path in the housing includes a confocal assembly to provide high definition imagery both at the surface of the tissue and of thin sections deep within the tissue. The confocal assembly includes scanning means, which preferably operate in a line-scanning format, although other scanning techniques may be used such as point scanning or Nipkow disk scanning.
In macroscopic mode, magnification changes occur by moving lenses in the housing, the endoscope tube, or both as the endoscope is moved closer to the object of interest. Changes in magnification also take place on switching between white light and laser light illumination. Filters, polarizers, and retarders are provided as appropriate to control the spectral and polarization characteristics of the illumination and imaging light.
The endoscope assembly includes an additional tube, or stage, that slides over the endoscope tube and removably attaches to the housing. The combined stage and endoscope tube are adapted for insertion into a body cavity through a cannula. The endoscope tube is movable with respect to the stage between an extended and a retracted position by drive means contained within the housing.
The stage has a window that provides an optical interface between the body cavity and the endoscope optics. The window can be placed directly against body tissue, and the endoscope tube can be moved in a direction perpendicular to the window to focus at different depths within the tissue. When the endoscope tube is in the retracted position in microscopic mode, the endoscope optics are focused at the outer surface of the stage window, which is in contact with the tissue surface; when the endoscope tube is extended, the focus moves away from the window to a depth below the surface of the tissue. A chamber filled with a liquid, preferably a saline solution, having a predetermined refractive index is provided between the stage window and the endoscope optics to approximately match the refractive index of body tissue. A reservoir is provided to allow the liquid-filled chamber to expand and contract as the endoscope tube is retracted or extended.
The stage also provides a sterile barrier between the body cavity and the endoscope tube. Because of its simplicity, the stage may be readily sterilized between uses or it may be disposable.
In the preferred embodiment of the invention, the optical images formed by the optical assemblies of the endoscope apparatus are focused onto CCD detectors and transmitted as electronic signals to a computer system. The computer system, in turn, communicates the digitized images via a network and/or telephone lines to a pathologist who may be remote from the patient. Consequently, the pathologist is capable of viewing the images through the endoscope on a real-time basis. Since the endoscopic imaging system of the present invention enables real-time pathological examination and diagnosis of suspect tissue, unnecessary biopsies and/or organ removal are prevented.